1 /*
2  * Copyright (C) 2012 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #include <vector>
20 
21 #include <android-base/stringprintf.h>
22 #include <input/AccelerationCurve.h>
23 #include <input/Input.h>
24 #include <input/VelocityTracker.h>
25 #include <utils/Timers.h>
26 
27 using android::base::StringPrintf;
28 
29 namespace android {
30 
31 /*
32  * Specifies parameters that govern pointer or wheel acceleration.
33  */
34 struct VelocityControlParameters {
35     // A scale factor that is multiplied with the raw velocity deltas
36     // prior to applying any other velocity control factors.  The scale
37     // factor should be used to adapt the input device resolution
38     // (eg. counts per inch) to the output device resolution (eg. pixels per inch).
39     //
40     // Must be a positive value.
41     // Default is 1.0 (no scaling).
42     float scale;
43 
44     // The scaled speed at which acceleration begins to be applied.
45     // This value establishes the upper bound of a low speed regime for
46     // small precise motions that are performed without any acceleration.
47     //
48     // Must be a non-negative value.
49     // Default is 0.0 (no low threshold).
50     float lowThreshold;
51 
52     // The scaled speed at which maximum acceleration is applied.
53     // The difference between highThreshold and lowThreshold controls
54     // the range of speeds over which the acceleration factor is interpolated.
55     // The wider the range, the smoother the acceleration.
56     //
57     // Must be a non-negative value greater than or equal to lowThreshold.
58     // Default is 0.0 (no high threshold).
59     float highThreshold;
60 
61     // The acceleration factor.
62     // When the speed is above the low speed threshold, the velocity will scaled
63     // by an interpolated value between 1.0 and this amount.
64     //
65     // Must be a positive greater than or equal to 1.0.
66     // Default is 1.0 (no acceleration).
67     float acceleration;
68 
VelocityControlParametersVelocityControlParameters69     VelocityControlParameters() :
70             scale(1.0f), lowThreshold(0.0f), highThreshold(0.0f), acceleration(1.0f) {
71     }
72 
VelocityControlParametersVelocityControlParameters73     VelocityControlParameters(float scale, float lowThreshold,
74             float highThreshold, float acceleration) :
75             scale(scale), lowThreshold(lowThreshold),
76             highThreshold(highThreshold), acceleration(acceleration) {
77     }
78 
dumpVelocityControlParameters79     std::string dump() const {
80         return StringPrintf("scale=%0.3f, lowThreshold=%0.3f, highThreshold=%0.3f, "
81                             "acceleration=%0.3f\n",
82                             scale, lowThreshold, highThreshold, acceleration);
83     }
84 };
85 
86 /*
87  * Implements mouse pointer and wheel speed control and acceleration.
88  */
89 class VelocityControl {
90 public:
91     VelocityControl();
~VelocityControl()92     virtual ~VelocityControl() {}
93 
94     /* Resets the current movement counters to zero.
95      * This has the effect of nullifying any acceleration. */
96     void reset();
97 
98     /* Translates a raw movement delta into an appropriately
99      * scaled / accelerated delta based on the current velocity. */
100     void move(nsecs_t eventTime, float* deltaX, float* deltaY);
101 
102 protected:
103     virtual void scaleDeltas(float* deltaX, float* deltaY) = 0;
104 
105     // If no movements are received within this amount of time,
106     // we assume the movement has stopped and reset the movement counters.
107     static const nsecs_t STOP_TIME = 500 * 1000000; // 500 ms
108 
109     nsecs_t mLastMovementTime;
110     float mRawPositionX, mRawPositionY;
111     VelocityTracker mVelocityTracker;
112 };
113 
114 /**
115  * Velocity control using a simple acceleration curve where the acceleration factor increases
116  * linearly with movement speed, subject to minimum and maximum values.
117  */
118 class SimpleVelocityControl : public VelocityControl {
119 public:
120     /** Gets the various parameters. */
121     const VelocityControlParameters& getParameters() const;
122 
123     /** Sets the various parameters. */
124     void setParameters(const VelocityControlParameters& parameters);
125 
126 protected:
127     virtual void scaleDeltas(float* deltaX, float* deltaY) override;
128 
129 private:
130     VelocityControlParameters mParameters;
131 };
132 
133 /** Velocity control using a curve made up of multiple reciprocal segments. */
134 class CurvedVelocityControl : public VelocityControl {
135 public:
136     CurvedVelocityControl();
137 
138     /** Sets the curve to be used for acceleration. */
139     void setCurve(const std::vector<AccelerationCurveSegment>& curve);
140 
141     void setAccelerationEnabled(bool enabled);
142 
143 protected:
144     virtual void scaleDeltas(float* deltaX, float* deltaY) override;
145 
146 private:
147     const AccelerationCurveSegment& segmentForSpeed(float speedMmPerS);
148 
149     bool mAccelerationEnabled = true;
150     std::vector<AccelerationCurveSegment> mCurveSegments;
151 };
152 
153 } // namespace android
154